Update 1.21-notes.md

doc/1.21-notes.md

@@ -61,6 +61,7 @@
 * Move a whole lot of item data over to components (likely including CCA item components and potentially even some Forge item capabilities)
 * Make more registries dynamic/datapackable, e.g. brews
 * Make verified multiblocks (alfheim portal frame, terra plate base, enchanter setup, gaia arena without beacon base) datapackable, but with plausability checks
+* Set up `package-info.java` with `@FieldsAreNonnullByDefault`, `@MethodsReturnNonnullByDefault`, and `@ParametersAreNonnullByDefault` (as Minecraft, Fabric API, and NeoForge do) to cut down the number of required `@NonNull` annotations everywhere
 
 ### Feature candidates (potentially breaking changes)
 * nice-to-have Patchouli features we could use, that are yet to be merged: